Remote Attach fails without message

[JeronimoMaggi]

VS Code Version: 1.95.3
Commit: f1a4fb1
Date: 2024-11-13T14:50:04.152Z
Electron: 32.2.1
ElectronBuildId: 10427718
Chromium: 128.0.6613.186
Node.js: 20.18.0
V8: 12.8.374.38-electron.0
OS: Linux x64 6.9.3-76060903-generic / Pop!_OS 22.04 LTS
Debugpy extension version: v2024.12.0

I'm setting up a generic remote attach config in my launch.json. When I click Start Debugging, I only get an error window with no message. Any way to know what is failing? The logs I found don't seem to have any info. If I intentionally break it in other ways, the window does show an appropriate error message.:

[karthiknadig]

@JeronimoMaggi Can you open the developer console to see what is going on? you can get to it from Help > Toggle Developer Tools, there might be error there.

[ozzy92]

I'm getting the same thing on a Mac with an auto generated config using the "Add Configuration..." button:

{
"name": "Python Debugger: Remote Attach",
"type": "debugpy",
"request": "attach",
"connect": {
"host": "localhost",
"port": 9000
},
"pathMappings": [
{
"localRoot": "${workspaceFolder}",
"remoteRoot": "."
}
]
}

I opened dev tools, what should I see? There's nothing in the console after trying to launch.

[karthiknadig]

@ozzy92 Can you share your full launch.json config?

[ozzy92]

I cut it down to just the one config, same issue:

{
    // Use IntelliSense to learn about possible attributes.
    // Hover to view descriptions of existing attributes.
    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Python Debugger: Remote Attach",
            "type": "debugpy",
            "request": "attach",
            "connect": {
                "host": "localhost",
                "port": 9000
            },
            "pathMappings": [
                {
                    "localRoot": "${workspaceFolder}",
                    "remoteRoot": "."
                }
            ]
        }
    ]
}

[karthiknadig]

Is there anything in the logs under these channels:

[ozzy92]

Python Debugger just repeats this when I try:
2024-12-09 11:56:55.945 [info] Resolving attach configuration with substituted variables 2024-12-09 11:56:55.947 [info] Connecting to DAP Server at: localhost:9000

I had a broken extension filling Extenship Host output, so I disabled it, those went away, same issue. Empty now.

[JeronimoMaggi]

The Python Debugger output just says:
2024-12-09 18:05:58.929 [info] Resolving attach configuration with substituted variables 2024-12-09 18:05:58.932 [info] Connecting to DAP Server at: localhost:5678

And also nothing on the Extension Host output other than:

2024-12-09 18:05:47.938 [info] ExtensionService#_doActivateExtension vscode.debug-auto-launch, startup: false, activationEvent: 'onStartupFinished'
2024-12-09 18:05:47.939 [info] ExtensionService#_doActivateExtension vscode.merge-conflict, startup: false, activationEvent: 'onStartupFinished'
2024-12-09 18:05:58.923 [info] ExtensionService#_doActivateExtension vscode.debug-server-ready, startup: false, activationEvent: 'onDebugResolve'

[karthiknadig]

Do you see an entry for ms-python.debugpy in the extension host logs?

[JeronimoMaggi]

Only these 2:

2024-12-09 18:05:47.295 [info] ExtensionService#_doActivateExtension ms-python.python, startup: false, activationEvent: 'onLanguage:python', root cause: ms-python.debugpy
2024-12-09 18:05:47.643 [info] ExtensionService#_doActivateExtension ms-python.debugpy, startup: false, activationEvent: 'onLanguage:python'

[karthiknadig]

Can you confirm that a server is running at localhost:5678? the port can vary based on what you have for the launch setting.

[JeronimoMaggi]

The problem was indeed on the server side, it was silently failing. The error window without a message was throwing me off, and I thought it was a debugpy issue. Having a message that says "Failed to connect" would be useful to debug it. Thank you for looking into this!

[ozzy92]

Same; debugger was waiting in a container without a port mapping, so it wasn't accessible. A message woulda helped!

[karthiknadig]

@connor4312 This looks like an issue with how the Debug Adapter Client handles cases where it needs to connect to remote hosts. We pass a DebugAdapterServer object back to VS Code, and if it fails to connect it should raise an issue in an obvious manner. Looks like connection failure issues are not surfaced properly.

https://github.com/microsoft/vscode-python-debugger/blob/27747d1a48203e7cbb642bb633650d9e25347872/src/extension/debugger/adapter/factory.ts#L60-L63